US 7530158 B2
A method is disclosed for fabricating a CPP read head for a magnetic disk drive having an electrical isolation layer. The method includes providing a first shield layer, depositing a sensor stack on the first shield layer, a CMP stop layer is deposited on the sensor stack, and a release layer is deposited a on the CMP stop layer. Photoresist material containing Si is deposited on the release layer, and the photoresist material is then patterned and then oxidized by Reactive Ion Etching to form a high temperature photomask. The electrical isolation layer is then deposited to surround the sensor stack using a high temperature deposition process. The read head is then continued as either an in-stack bias sensor with ‘draped shield’ variation, or a hard bias stabilization variation.
1. A method for fabricating a CPP read head for a magnetic disk drive having an electrical isolation layer, comprising:
A) providing a first magnetic shield layer;
B) depositing a sensor stack on said first magnetic shield layer;
C) depositing a first CMP stop layer on said sensor stack;
D) depositing a release layer on said first CMP stop layer;
E) depositing photoresist material containing Si on said release layer;
F) patterning said photoresist material to form protected areas in the underlying materials;
G) oxidizing said photoresist material by use of Reactive Ion Etching to form a high temperature photomask;
H) depositing said electrical isolation layer to surround said sensor stack using a high temperature deposition process, where said high temperature photomask protects said protected areas during said high temperature deposition process;
I) depositing a draped magnetic shield material layer on said electrical isolation layer;
J) depositing a second CMP stop layer on said draped magnetic shield material layer; and
K) planarizing said isolation layer and said draped magnetic shield material layer to the level of said sensor stack to form a planarized structure.
2. The method of fabricating a CPP read head of
said sensor stack is an in-stack bias sensor.
3. The method for fabricating a CPP read head of
L) depositing a second magnetic shield layer upon said planarized structure.
4. The method for fabricating a CPP read head of
said planarizing of K) is done by CMP processes and said first and second CMP stop layers act to limit the planarizing action.
5. The method for fabricating a CPP read head of
said first CMP stop layer is diamond-like-carbon.
6. The method for fabricating a CPP read head of
said release layer also acts as a secondary mask layer.
7. The method for fabricating a CPP read head of
said release layer is spin-on polymide.
8. The method for fabricating a CPP read head of
said high temperature deposition process of H) includes a process chosen from the group consisting of Chemical Vapor Deposition, Atomic Layer Deposition, Plasma Enhanced Chemical Vapor Deposition or High Temperature Sputtering.
9. The method for fabricating a CPP read head of
oxidizing of said photoresist material by use of Reactive Ion Etching of G) is done by using a gas chosen from the group consisting of oxygen and carbon dioxide.
1. Field of the Invention
The present invention relates generally to fabrication of electronic components and particularly to fabrication of components for disk drive heads.
2. Description of the Prior Art
Photomasking is a technique which is commonly used in making electronic components. It is especially useful in many patterned deposition processes in which layers are deposited one upon another, but there may be a need to block off certain areas from the deposition of one or more layers. This is commonly done by depositing photomask material, usually a photo-resist material, which hardens when exposed to certain wavelengths of light, to mask off certain areas. Unexposed areas of the photoresist material are then removed. After the deposition of the layer is done, the photomask is removed, or lifted off, taking the deposition material with it to leave an un-coated portion.
Conventional prior art photomask materials are useful for certain operations which can be accomplished within a range of lower temperatures. However, certain other operations which are becoming more widely used, must be conducted at higher temperatures, for which these prior art photomask materials are not suited.
One example which illustrates the limitations of prior art photomask materials can be found in the fabrication of disk drive heads. TMR (Tunnel Magnetoresistance) and other CPP (Current Perpendicular to the Plane) read head devices utilize a dielectric layer to confine electrical current to the sensor area. Since practical CPP devices in the deep submicron regime require self-aligned processing for patterning and isolation, the patterning techniques used must be compatible with the deposition techniques for each of the layers. Conventional photo processing materials poorly tolerate temperatures in excess of 130 degrees C. limiting applicable deposition techniques for the dielectric layer to those that are PVD (Physical Vapor Deposition)-based. PVD-based deposition techniques lack the conformality and low defect density of CVD (Chemical Vapor Deposition) techniques such as ALD (Atomic Layer Deposition). A complete review of ALD-based deposition techniques and their benefits is described by Ritala and Leskelä in Handbook of Thin Film Materials, H. S. Nalwa, Ed., Academic Press, San Diego (2001) Vol 1, Chapter 2 (ISBN 0-12-512908-4).
Thus there is a need for a photomask material which will not degrade at temperatures necessary for CVD processes. There is a further need for a method of fabrication of disk drive read heads which uses high temperature photomasks when using high temperature processes such as ALD.
A preferred embodiment of the present invention is a method for fabricating a CPP read head for a magnetic head of a hard disk drive having an electrical isolation layer. The method includes providing a first magnetic shield layer, and depositing a sensor stack on the first magnetic shield layer. Next, a CMP (Chemical Mechanical Polishing) stop layer is deposited on the sensor stack, and a release layer is deposited on the CMP stop layer. Photoresist material containing Si is deposited on the release layer, and the photoresist material is then patterned to form protected areas in the underlying materials. The photoresist material is then oxidized by use of Reactive Ion Etching (RIE) to form a high temperature photomask and to transfer the photo image into the release layer. Ion milling or RIE is then used to transfer this image into the sensor stack. The electrical isolation layer is then deposited to surround the sensor stack using a high temperature deposition process such as Chemical Vapor Deposition, where the high temperature photomask protects areas of the underlying material during the high temperature deposition process. The present invention is compatible with processes that require higher temperature than those allowed by prior art photomasks, and these processes may produce better conformality and fewer defects. These temperatures enable the use of ALD technology using TMAl (TriMethylAluminum) and Water precursors to grow Al2O3 with excellent electrical properties and step coverage. Temperatures substantially below this increase the concentration of Carbon in the film, degrading its properties. In addition, the use of low temperatures in commercially-available ALD reactors cause premature delamination of the as-grown films from the reactor walls, making the process not commercially viable.
If the sensor is an in-stack bias sensor, a draped magnetic shield material layer is deposited on the electrical isolation layer and a second CMP stop layer is deposited on the draped magnetic shield material layer. The isolation layer and the draped magnetic shield material layer are then planarized to the level of the sensor stack to form a planarized structure, upon which a second magnetic shield layer is deposited.
If the sensor is an external bias sensor, a hard bias material layer is deposited on the electrical isolation layer and a second CMP stop layer is deposited on the hard bias material layer. The isolation layer and the hard bias material layer are then planarized to the level of the sensor stack to form a planarized structure, upon which a second magnetic shield layer is deposited.
It is an advantage of the present invention that it provides a photomask material that is useful above 130 degrees C.
It is a further advantage that the present invention provides a photomask material that can be used with CVD processes.
It is a yet further advantage that the present invention provides a photomask material that can be used in the fabrication of CPP read heads having an insulation layer which is deposited by using ALD.
It is another advantage that the present invention is compatible with processes that require higher temperature than those allowed by prior art photomasks, and these processes may produce better conformality and fewer defects.
These and other features and advantages of the present invention will no doubt become apparent to those skilled in the art upon reading the following detailed description which makes reference to the several figures of the drawing.
The following drawings are not made to scale as an actual device, and are provided for illustration of the invention described herein.
This invention is a photomask suitable for use with relatively high-temperature deposition processes such as ALD (Atomic Layer Deposition), and other CVD (Chemical Vapor Deposition) techniques. For purposes of this patent application, the photomask of the present invention shall be referred to as high temperature photomask, and referred to by the element number 50.
The high temperature photomask uses Si-containing photoresist which has been spin-coated and baked on to the wafer using a procedure recommended by its manufacturer. A suitable resist is called TIS 51-23il and is manufactured by ARCH Microelectronic Materials.
Following the baking step, the photoresist is then exposed using the wavelength of light which is recommended for the chosen photoresist. This exposed photoresist is then developed according to the manufacturers' recommendations to remove unexposed photoresist areas and create a robust photoresist mask.
Reactive Ion Etching is then utilized to oxidize the photoresist and to transfer the photoresist image into the underlying layers such as spin-on polymide and DLC (diamond-like carbon) layers. This step forms a hard photoresist mask layer which will later stand up to ion milling and high temperature processing. It is especially useful for the fabrication of CPP read head devices using self-aligned patterning of the sensor stack and the deposition of a dielectric current confinement layer using elevated temperature techniques such as ALD.
A CPP sensor such as a TMR (Tunnel Magnetoresistive) sensor is patterned utilizing a tri-layer structure consisting of DLC (Diamond-Like-Carbon), spin-on polymide and the Si-containing Photoresist. The Si-containing photoresist is exposed to an oxygen-containing RIE to create a significant amount of SiO2. This structure is sufficiently robust to tolerate ALD deposition of Aluminum Oxide for the current confinement layer at a temperature in excess of 170 degrees C. This technique is compatible with both the ISB (In Stack Bias) and ICJ (Insulating Contiguous Junction) approaches to read head design. The ALD-synthesized confinement layer has excellent step coverage and film quality, enabling superior control and reduced thickness of the second magnetic shield to sensor (ISB) or Hard Bias to sensor (ICJ) distance. This enables stable device performance and superior shielding.
As an illustration of the use of the high temperature mask, a CPP read sensor will be discussed below, and the stages of fabrication of the CPP read sensor will be described and shown in
As mentioned above, it is desirable for the CPP read head sensor stack to be surrounded with an electrical isolation layer, which prevents the electrical current from taking undesired paths, and causing short circuits. Since the current in this CPP design is perpendicular to the plane, it is desired to have the isolation layer surround the sides of the sensor. The preferred insulation material for this application is dielectric material such as alumina (Al2O3) or SiO2, which are best deposited using high temperature processes such as ALD, and thus this is an application of the high temperature photomask 50 of the present invention.
A magnetic hard disk drive 2 is shown generally in
A read sensor 40 is sandwiched between a first magnetic shield, designated as S1 30 and a second magnetic shield S2 34, and these elements together make up the read head 28. In this configuration of read head 28 where Current is Perpendicular to the Plane (CPP), shields S1 30 and S2 34 act as electrical leads supplying current to the read sensor 40 which lies between them. An insulation layer 32 also separates the S1 30 and S2 34 electrical leads in the area behind the read sensor 40, so that they do not short out along their length. The magnetic head 14 flies on an air cushion between the surface of the disk 4 and the air bearing surface (ABS) 24 of the slider 16.
The stages in the fabrication of the read head 28 using the high temperature photomask 50 are shown in
Upon the spin-on polymide layer 56, a layer of Si-containing photoresist 58 is spin-coated and baked on to the wafer using a procedure recommended by its manufacturer. A suitable resist is called TIS 51-23 il and is manufactured by ARCH Microelectronic Materials. The Si-containing photoresist 58 is then exposed using the wavelength of light which is recommended. This Si-containing photoresist 58 is then developed according to the manufacturers recommendations, and the excess photoresist is removed to form the photomask pattern 60 shown in
As shown in
There are two variations possible in the following stages. The first will be referred to as the “in-stack bias sensor with ‘draped magnetic shield’” 72 variation, which will be discussed with reference to
As shown in
The second CPP read head variation shall be called the “hard bias stabilization variation” 76, and will be discussed with reference to
As seen in
If device performance requires a particular read gap thickness, a combination top electrode/spacer layer 82 may be deposited here, however this step is entirely optional. In a CPP structure of any sort, this electrode/spacer layer 82 should be a metal which is compatible with the many requirements for a finished recording head device—electrical conductivity, chemical compatibility, hardness, corrosion resistance etc. Again, one skilled in the art could readily choose many different materials.
While the present invention has been shown and described with regard to certain preferred embodiments, it is to be understood that modifications in form and detail will no doubt be developed by those skilled in the art upon reviewing this disclosure. It is therefore intended that the following claims cover all such alterations and modifications that nevertheless include the true spirit and scope of the inventive features of the present invention.
THIS CORRESPONDENCE CHART IS FOR EASE OF UNDERSTANDING AND INFORMATIONAL PURPOSES ONLY, AND DOES NOT FORM A PART OF THE FORMAL PATENT APPLICATION.